Last.fm - The world's largest online music service. Listen online, find out more about your favourite artists, and get music recommendations, only at Last.fm
Maloja - Simple self-hosted music scrobble database to create personal listening statistics.
Last.fm Scrobbler - Scrobble music all around the web!
foo_scrobble - foobar2000 component for last.fm scrobbling
ListenBrainz - Open source music website that allows users to import their listen history.
Spotify - Map shows when two people play same song at same time